Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison
It might be that if it goes empty, the lines are empty...so nothing is going to come out, since there is air in the lines (I'm guessing). The intent I believe, is to keep ink in the lines (keep it primed) so that you don't have issues when loading the new ink cartridge.
I use fluorescent blacklights for exposure so I don't need super dense positives. Thanks.
I only use the matte black cartridge for making my film.
...it is dye based, so make sure the film you're using is dye compatible. Some waterproof films are not.
Wow, not questioning this, but surprised. For years, I found that most clear "standard" films (now harder to find) were only surely compatible with dye based inks, while the milky "waterproof" films and their inherent higher d-min was the main choice for pigment ink users.